Shaped structures such as pipe and pipe fittings of organic polymeric material such as polyethylene have become widely known and used for diverse purposes such as for conveying fluids. Piping systems of organic polymeric material have been found to be desirable especially in view of the ease with which such systems may be fabricated. For example, pipe fittings and pipe may easily be assembled together by utilizing chemical solvents, adhesives or heating treatments for joining these pieces, e.g., polyethylene pipe fittings may be joined to polyethylene pipe by heating the fitting and the pipe before assembly to melt the polyethylene at the region or surface of each piece to be contacted followed by mating the heated surfaces of each piece and cooling the heated pieces whereby to effect fusing of the polyethylene to provide a structure of integral or unitary construction. Such pipe and pipe fittings have been found to be especially useful in relining sewer mains.
Existing sewer mains of, for example, concrete, clay, or cast iron pipe, often become unserviceable because a pipe section either decays or is physically damaged as by breaking due to dynamic earth stresses acting thereon. Rehabilitating unserviceable sewers by replacing defective sewer components is extremely difficult and expensive. These drawbacks can be minimized or avoided by inserting polyethylene pipe into existing sewer mains. This is easily accomplished by effecting only a few excavations at widely spaced points along a sewer main and penetrating the main at these points and inserting thereinto a continuous length of polyethylene pipe. These lengths of polyethylene pipe may be connected at their respective ends by conventional fusing techniques to provide a continuous pipe encompassed within the existing sewer main. A method and apparatus for relining sewer pipe are disclosed in, for example, U.S. Pat. No. 3,602,263.
Joining a branch service line to the continuous plastic pipe inserted in the sewer main presents a difficult problem. It is often necessary, and sometimes unavoidable, to destroy and remove a section of the branch line in order to provide a means of access for penetrating through the wall of the continuous plastic pipe in the sewer main which is necessary for connecting the branch line to the renewed sewer main. The foregoing does, however, require replacement sections of the branch line which usually entails extensive, expensive and undesirable excavation work in often crowded locations such as public thoroughfares which leads to undesirable public inconvenience. Accordingly, the object of the present invention is to provide a core element suitable for readily and easily joining a branch line to a plastic pipe in a sewer main.